Amusingly I was the competent FOSS guy brought in to our council, after a year or so getting into the reality of the environment, I actually recommended a Microsoft EA, rather than the muddle of Linux/Windows we were using. I couldn't do *everything* and there was minimal scope for investment in new staff / training.
The grandparent post and the guy at hampshire is absolutely correct, Open Source desktop / office offers no *cost* advantage in a typical council. Working in IT for a council is an absolute slog, the app portfolio is in the hundreds, all of which are "business critical" to some team or other. Faffing around with a Linux based Desktop or Swapping out Microsoft Office is a poor use of time, which you'll soon realise is impossible without either utilising Windows licenses anyway for a terminal services solution for non-compatible apps or where App XYZ uses VBA for letter generation / mail merge etc. Before you know it, your spending more in time working out who can and can't use OpenOffice than the license itself costs. Office is one app, and in itself it's not that business critical, except for perhaps Outlook/Exchange for which there hasn't been an obvious candidate for an OS replacement.
We do of course use Open Source where it makes sense. GIS is very much going open-source, we have a few dozen CentOS/Redhat Servers (firewalls/file servers/tomcat etc.) , including our Council Tax system running on Linux. We are absolutely not scared of Open Source or Linux, but it just has a limited role on the desktop.